This section is intended to provide a background or context to the invention recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the present invention and is not admitted to be prior art by inclusion in this section.
Temperature-controlled storage devices (e.g., a refrigerator, freezer, refrigerated merchandiser, display case, etc.) are used in a wide variety of commercial, institutional, and residential applications for storing and/or displaying refrigerated or frozen objects. Many temperature-controlled storage devices have a display case door (e.g., a door with an insulated glass panel) through which objects within the temperature-controlled storage device can be viewed.
Conventional insulated glass panels typically include multiple parallel panes with a layer of gas between the panes. The gas is generally air or a noble gas (e.g., Argon, Krypton, etc.) which functions as a thermal insulator to reduce heat transfer through the panel. In conventional insulated glass panels, the pressure of the air or gas between the panes is equal or substantially equal to atmospheric pressure. Reducing the pressure of the air or gas between the panes would cause atmospheric pressure to apply a large force (e.g., thousands of pounds of force) to the surface of the panel. Such a force is likely to bend or break an insulated glass panel, especially if the panel is relatively thin.
Vacuum insulated glass is a type of insulated glass panel which uses an evacuated space or gap between parallel panes of glass as an insulating layer. The manufacture of vacuum insulated glass typically involves sealing parallel panes of glass to each other at their edges (e.g, using glass solder) and drawing a vacuum in a thin gap between the parallel panes. Such a manufacturing process requires the panes of glass to be held at a high temperature while the edge seal is formed in order to ensure proper bonding.
Conventional vacuum insulated glass panels use panes of non-tempered glass. Non-tempered glass typically has an improved flatness relative to tempered glass, which allows the gap between panes to have a substantially uniform thickness. However, non-tempered glass is typically more fragile than tempered glass and fractures into larger shards when broken. Using tempered glass in a vacuum insulated glass panel could have significant durability and safety advantages. However, the typical manufacturing process used to create vacuum insulated glass panels prevents the use of tempered glass because the high temperatures used to form the edge seal removes any tempering from the glass. For these reasons, a vacuum insulated glass panel constructed from tempered glass has not been successfully implemented.